Missions to the lunar vicinity are costly, partially because all vehicles for past lunar missions have been constructed for the missions, and launched on very large launch vehicles that are required to orbit both the spacecraft and the upper stage necessary to provide the additional velocity for the spacecraft to leave Earth orbit and travel to the Lunar vicinity. Since no current launch vehicle is large enough to orbit both a human piloted spacecraft and an upper stage sufficiently capable to put the spacecraft on a translunar trajectory, the resulting costs for a lunar mission has been too high to warrant sending crews to the Moon since 1972. The present invention is intended to reduce costs of lunar missions so that these missions would cost little or more than current missions in Earth orbit.
Another problem is that spacecraft intended for human pilots and passengers are very expensive, and any lunar mission that effectively consumes such a spacecraft during a normal mission has a high cost.
Another problem is that spacecraft designed for operation in Earth orbit do not normally contain all systems required for lunar missions, and modification of a spacecraft intended for flight in Earth orbit for lunar operations would be costly and moreover these additional lunar systems may reduce the spacecraft's operations for Earth orbit missions.
Another problem is that Earth-orbit rendezvous architectures for lunar missions, which require the Lunar Crew Return spacecraft (CRS) to rendezvous and dock with the remaining part of the lunar spacecraft in Earth orbit, before heading to the lunar vicinity, require that both launches occur in a relatively short period of time. The requirement for dual launches in a short period significantly increases mission risk as it is normal for launches to be delayed, particularly from spaceports such as Kennedy Space Center which experience a good deal of poor weather. For example, if the second launch is delayed, by weather or last minute issues with the launch vehicle or spacecraft, while the first spacecraft is in orbit, this may create a Hobson's choice of either returning the first spacecraft to Earth from Earth orbit (thereby wasting the first launch and delaying the entire mission to the Moon), or rushing the second launch, possibly by waiving requirements (as NASA has done in the past under schedule pressure) and thereby increasing the risk of a failed launch.